[compiler] Remove broken support for undetectable strings.

src/full-codegen/arm/full-codegen-arm.cc

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "src/v8.h"
 
 #if V8_TARGET_ARCH_ARM
 
 #include "src/code-factory.h"
 #include "src/code-stubs.h"
@@ skipping 5014 matching lines @@
 
   Factory* factory = isolate()->factory();
   if (String::Equals(check, factory->number_string())) {
     __ JumpIfSmi(r0, if_true);
     __ ldr(r0, FieldMemOperand(r0, HeapObject::kMapOffset));
     __ LoadRoot(ip, Heap::kHeapNumberMapRootIndex);
     __ cmp(r0, ip);
     Split(eq, if_true, if_false, fall_through);
   } else if (String::Equals(check, factory->string_string())) {
     __ JumpIfSmi(r0, if_false);
-    // Check for undetectable objects => false.
     __ CompareObjectType(r0, r0, r1, FIRST_NONSTRING_TYPE);
-    __ b(ge, if_false);
-    __ ldrb(r1, FieldMemOperand(r0, Map::kBitFieldOffset));
-    __ tst(r1, Operand(1 << Map::kIsUndetectable));
-    Split(eq, if_true, if_false, fall_through);
+    Split(lt, if_true, if_false, fall_through);
   } else if (String::Equals(check, factory->symbol_string())) {
     __ JumpIfSmi(r0, if_false);
     __ CompareObjectType(r0, r0, r1, SYMBOL_TYPE);
     Split(eq, if_true, if_false, fall_through);
   } else if (String::Equals(check, factory->boolean_string())) {
     __ CompareRoot(r0, Heap::kTrueValueRootIndex);
     __ b(eq, if_true);
     __ CompareRoot(r0, Heap::kFalseValueRootIndex);
     Split(eq, if_true, if_false, fall_through);
   } else if (String::Equals(check, factory->undefined_string())) {
@@ skipping 393 matching lines @@
   DCHECK(interrupt_address ==
          isolate->builtins()->OsrAfterStackCheck()->entry());
   return OSR_AFTER_STACK_CHECK;
 }
 
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_TARGET_ARCH_ARM